Apparatus for dampening erratic vertical movements of well tools

ABSTRACT

In the preferred embodiment of the present invention disclosed herein, a well tool is dependently coupled to a suspension cable having a large number of relatively stiff, but flexible, laterally projecting members distributed along the lower portion of the cable and adapted to occupy a substantial portion of the annular space between this lower cable portion and the surrounding walls of a well bore. In this manner, as the well tool is being moved upwardly through a fluid-filled well bore, these outwardly projecting members will induce a viscous drag which will be effective to at least dampen vertical oscillatory movements of the tool and cable that will otherwise be induced by unpredictable differences in the frictional drag of the tool and cable along the well bore wall.

United States Patent [72] Inventor Jean Louis Bernard Houston, Tex. [21] Appl. No. 22,931 [22] Filed Mar. 26, 1970 [45] Patented Dec. 21, 1971 [73] Assignee Schlumberger Technology Corporation New York, N.Y.

[54] APPARATUS FOR DAMPENING ERRATIC VERTICAL MOVEMENTS 0F WELL TOOLS 10 Claims, 4 Drawing Figs.

[52] 11.5. C1 166/241, 166/170, 57/143 [51] 1lnt.Cl E211 17/10 [50] Field of Search 57/143, 145,147,148,166,153;166/170,173,241

[56] References Cited UNITED STATES PATENTS 1,882,905 10/1932 Reiner 57/143 2,753,833 7/1956 Tinsley t. 57/143X Primary Examiner-David H. Brown Attorneys-Ernest R. Archambeau, Jr., David L Moseley.

Edward M. Roney, William R. Sherman and Stewart Fv Moore ABSTRACT: 1n the preferred embodiment of the present invention disclosed herein, a well tool is dependently coupled to a suspension cable having a large number of relatively stiff, but flexible, laterally projecting members distributed along the lower portion of the cable and adapted to occupy a substantial portion of the annular space between this lower cable portion and the surrounding walls of a well bore. ln this manner, as the well tool is being moved upwardly through a fluid-filled well bore, these outwardly projecting members will induce a viscous drag which will be effective to at least dampen vertical oscillatory movements of the tool and cable that will otherwise be induced by unpredictable differences in the frictional drag of the tool and cable along the well bore wall.

PATENTEDBEC21 HT! F/ GI Jean L. Bernard /NVEN7OR APPARATUS FOR DAMPENING ERRATIC VERTICAL MOVEMENTS F WELL TOOLS In conducting well completion operations with various types of cable-suspended well tools, it is fairly common for the tool to move erratically upwardly and downwardly even as the cable is being retrieved at a uniform speed. Those skilled in the art will, of course, appreciate that this erratic motion is induced, at least in part, by variations in the frictional drag encountered by the well tool as it moves along the walls of the well bore through which it is passing. Thus, a momentary increase in this frictional drag will produce a corresponding elongation of the suspension cable which will ultimately cause the tool to be suddenly jerked upwardly once either the frictional drag decreases or the resilient force induced in the cable by its elongation exceeds the frictional drag. As a result, even though the suspension cable is being retrieved at a uniform speed, the tool will successively be jerked upwardly and then momentarily halted in an erratic manner. It is readily apparent, of course, that such erratic movements of the well tool will make it difficult to determine with accuracy the depth at which the tool is at any particular moment. Moreover, where the well tool is performing a logging operation, the resulting logging record will be impaired by these erratic motions.

Accordingly, it is an object of the present invention to provide new and improved apparatus for regulating the velocity of a cable-suspended tool in such a manner as to at least dampen erratic oscillations of the cable coupled thereto.

This and other objects of the present invention are attained by arranging a plurality of laterally projecting, somewhat flexible, elements along the lower portion of a suspension cable immediately above a well tool dependently suspended therefrom. In this manner, when the cable is moved upwardly for returning the well tool through a fluid-containing well bore to the surface, these stiffened lateral projections will provide a sufficient impediment or frictional drag to the lower end of the cable that erratic movements of the well tool will be substantially dampened.

The novel features of the present invention are set forth with particularity in the appended claims.

The invention, together with further objects and advantages thereof, may be best understood by way of the following description of exemplary apparatus employing the principles of the invention as illustrated in the accompanying drawings, in which:

FIG. 1 depicts a preferred embodiment of the present invention as it may be employed during the course of a typical well completion operation;

FIG. 2 is an enlarged view of one embodiment of a cable arranged in accordance with the principles of the present invention; and

FIGS. 3 and 4 are enlarged views of alternative arrangements of the present invention.

Turning now to FIG. 1, a well tool is depicted within a well bore, such as a borehole 11, as the tool is being moved upwardly therethrough by means of a typical suspension cable 12 such as that shown in US. Pat. No. 3,259,675 granted to William E. Bowers. To illustrate a typical operation in which the present invention will be of particular utility, the well tool 10 is assumed to be a logging tool adapted for measuring one or more parameters which are characteristic of various properties of the earth formations traversed by the borehole ll. Accordingly, as depicted in the Bowers patent, the suspension cable 12 includes one or more electrical conductors coaxially enclosed within a tubular sheath of braided steel strands arranged for protecting the electrical conductors as well as to provide sufficient strength for supporting the well tool 10 therebelow. As will subsequently be explained in detail, a plurality of outwardly extending lateral projections, as at 13, are arranged, preferably in a helical pattern, along a substantial length of the lower portion of the suspension cable 12. If desired, the outstanding projections l3 may have a length about equal to the radius of the borehole 11. In this manner, as the tool 110 is being pulled upwardly through the borehole ll,

the added viscous drag of the outstanding projections 13 with the borehole fluids will tend to maintain the cable 12 in a stretched condition and thereby substantially reduce or eliminate erratic vertical movements of the tool.

In FIG. 2, an enlarged cross-sectional view is shown of one arrangement of a cable 20 incorporating the principles of the present invention. As illustrated, the otherwise typical logging cable 20 is modified by securing a plurality of fairly stiff wires or stiff fibers, as at 21, around the circumference of the cable so as to maintain these wires in a generally outstanding position in relation to the cable. In the preferred manner of accomplishing this, as the cable 20 is being manufactured, the wires 21 are laid transversely across the inner layer of armor strands 22; and, as the outer layer of armor strands 23 is being wound onto the cable, the wires are doubled so as to be captured at their midportions between the inner and outer armor layers and leave the ends of the wires extending outwardly. Although a doubled wire can, of course, be secured under each strand of the outer armor layer 23, a helical configuration of the wires 21 (as shown in FIG. 1) can be achieved as shown in FIG. 2 by securing the wires at longitudinally spaced intervals under only selected ones of the outer armor strands and letting the usual twist of these strands determine the heli cal pattern.

Those skilled in the art will, of course, appreciate that many logging tools require the placement of an electrode at an intermediate location on the cable. In such situations, the logging cable is coupled to a so-called bridle" which is in turn coupled to the logging tool. The bridle, as shown at 30 in FIG. 3, is typically arranged with the electrical conductors 31 coaxially arranged around a central load-supporting stranded cable 32 and encased within a suitable tubular insulating sheath 33. It will be recognized, therefore, that some other provisions must be made to secure outstanding drag members to the bridle 30. Accordingly, in one manner of accomplishing this, a plurality of outstanding stiff wires 34 can be embedded in a number of annular discs, as at 35, which are adapted to be stacked along the length of the bridle 30 to provide a sufficient number of the drag-inducing wires. Alternatively, as shown by the bridle 40 in FIG. 4, a plurality of outstanding stiffened wires 41 can be mounted onto the bridle by securing the doubled wires to a braided tubular sheath 42 fitted around the external insulation 4l3.

Accordingly, it will be appreciated that by disposing a plurality of outstanding drag-inducing members along the lower portion of a suspension cable, as a well tool coupled thereto is being pulled upwardly through a fluid-containing well bore a substantial drag will be imposed on the cable to maintain it in a stretched condition. In this manner, erratic oscillatory movements of the tool which have heretofore been a significant problem in the art will be substantially reduced if not altogether eliminated.

While particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made without departing from this inven tion in its broader aspects; and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. Well bore apparatus comprising: an electrical cable adapted to support a well tool; a well tool dependently coupled to said cable and adapted to be moved thereby through a well bore; and a plurality of outstanding stiff lateral projections operatively arranged at angularly spaced intervals around at least the lower length of said cable adjacent to said well tool and adapted for inducing a viscous drag to dampen erratic movements of said well tool upon upward movements of said cable for pulling said well tool through a fluid-containing well bore.

2. The well bore apparatus of claim ll wherein said lateral projections are of a somewhat flexible material.

3. The well bore apparatus of claim ll wherein said lateral projections are arranged in a generally helical pattern around said lower length of said cable.

an outer sheath and said lateral projections are secured to said armor sheath.

8. The well bore apparatus of claim 7 wherein said lateral projections are short pieces of stiff wire.

9. The well bore apparatus of claim 1 further including a tubular sheath disposed around said cable and wherein said lateral projections are secured to said tubular sheath.

10. The well bore apparatus of claim 9 wherein said lateral projections are short pieces of stifi' wire. 

1. Well bore apparatus comprising: an electrical cable adapted to support a well tool; a well tool dependently coupled to said cable and adapted to be moved thereby through a well bore; and a plurality of outstanding stiff lateral projections operatively arranged at angularly spaced intervals around at least the lower length of said cable adjacent to said well tool and adapted for inducing a viscous drag to dampen erratic movements of said well tool upon upward movements of said cable for pulling said well tool through a fluid-containing well bore.
 2. The well bore apparatus of claim 1 wherein said lateral projections are of a somewhat flexible material.
 3. The well bore apparatus of claim 1 wherein said lateral projections are arranged in a generally helical pattern around said lower length of said cable.
 4. The well bore apparatus of claim 3 wherein said lateral projections are of a somewhat flexible material and have a length about equal to the radius of a well bore in which said apparatus is to be employed.
 5. The well bore apparatus of claim 1 further including a plurality of annular members arranged along said cable and wherein said lateral projections are secured to said annular members.
 6. The well bore apparatus of claim 5 wherein said lateral projections are short pieces of stiff wire.
 7. The well bore apparatus of claim 1 wherein said cable has an outer sheath and said lateral projections are secured to said armor sheath.
 8. The well bore apparatus of claim 7 wherein said lateral projections are short pieces of stiff wire.
 9. The well bore apparatus of claim 1 further including a tubular sheath disposed around said cable and wherein said lateral projections are secured to said tubular sheath.
 10. The well bore apparatus of claim 9 wherein said lateral projections are short pieces of stiff wire. 